JP5556698B2 - Battery assembly - Google Patents

Description

  The present invention relates to an assembled battery device having a stable output characteristic region in which voltage fluctuation is small with respect to a change in SOC (state of charge).

  The prior art described in Patent Document 1 is a lithium ion battery having characteristics capable of ensuring a flat charge / discharge capacity range. This lithium ion battery was charged and discharged with a current having a current value of 1 C over a capacity range of 50% or more of the entire theoretical electric capacity (for example, a capacity range corresponding to 20% to 80% of the theoretical electric capacity). In some cases, the variation of the inter-terminal voltage has a characteristic capable of ensuring a capacity range in which the voltage is 0.2 V or less.

  Therefore, according to this lithium ion battery, at least within a flat charge / discharge capacity range, the voltage change can be reduced and charged / discharged, and stable output characteristics (IV characteristics) with small output fluctuations can be obtained. .

JP 2009-129644 A

  In the technique described in Patent Document 1, SOC estimation by current integration is performed in a voltage change flat region (region where the voltage between terminals is 3.25 to 3.45 V) in which output fluctuation is small, and a change in electric quantity of the voltage between terminals is performed. When the rate exceeds the threshold, SOC estimation is performed using the voltage. That is, when the SOC is 15% to 95%, for example, the SOC estimation is performed by integrating the current. Therefore, this method generally has a larger error than the calculation of the electric quantity by the voltage, and the accuracy of the SOC detection is not preferable. is there.

  Therefore, in order to ensure the accuracy of SOC detection, it is necessary to perform SOC correction in a state close to full charge or complete discharge except for the SOC range of 15% to 95%. However, during actual charging / discharging, it takes time to fully charge or discharge, and depending on the usage conditions, there is a possibility that the battery may be used in a region other than full charging or discharging. High accuracy detection of SOC in the region becomes a problem.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to enable a highly accurate detection of a charging state in a stable output characteristic region in which voltage fluctuation is small with respect to a change in SOC. The object is to provide a battery device.

In order to achieve the above object, the present invention employs the following technical means. That is, the invention relating to the assembled battery device of claim 1 includes a plurality of secondary batteries having charging characteristics having a low change region in which a voltage change width with respect to a charging rate is a predetermined value or less, and charging to the secondary battery. At the time, using a voltage, current detected for the secondary battery, and a calculation device that calculates the charging rate stored in the secondary battery,
When the charging is performed in the low change region, the arithmetic unit sets the voltage when the voltage change rate exceeds a predetermined threshold for a predetermined time, or when the voltage change rate for the electric voltage is set for a predetermined time. When the threshold value is exceeded, the detected value of the charging rate of the secondary battery is determined to be a specified value of the charging rate associated in advance with the predetermined threshold value.

According to the present invention, when a predetermined condition is satisfied that the electrical change rate of time change rate or voltage of the voltage corresponding to the respective provision has been corresponded beforehand charging rate detected value of the charging rate of the secondary battery By determining the value, the charging rate of the secondary battery can be detected. Therefore, it is possible to provide an assembled battery device that enables highly accurate detection of the charging rate in a region of stable output characteristics in which voltage fluctuation is small with respect to a change in SOC.

The invention according to claim 2 includes a plurality of secondary batteries having a charging characteristic including a low change region in which a voltage change with respect to a charging rate is equal to or less than a predetermined value, and charging the secondary battery An arithmetic unit that calculates the charge rate stored in the secondary battery using the voltage and current detected for the secondary battery, and
When performing the charging in the low change region, the arithmetic unit determines the detection value of the charging rate of the secondary battery when the time change rate of the voltage exceeds a predetermined threshold for a predetermined time. The charging rate value is calculated from a relational expression that is previously associated with the threshold value and that is satisfied between the time change rate of the voltage and the charging rate .

According to the present invention, when a predetermined condition is satisfied that the time rate of change of voltage corresponding, during the detection value of the charging rate of the secondary battery, and the time rate of change corresponded beforehand et al are voltage and charging rate by determining the value of the charging rate calculated from the relational expression is satisfied, it is possible to detect the charging rate of the secondary battery. Therefore, it is possible to provide an assembled battery device that enables highly accurate detection of the charging rate in a region of stable output characteristics in which voltage fluctuation is small with respect to a change in SOC.

According to claim 3, computing device, during charging, to detect the displacement amount of the charging rate is the difference between the charging rate between the secondary cell from the charging rate determined for each of the secondary batteries, of the charging rate It is characterized in that the charging current is reduced for the secondary battery selected to suppress the deviation amount.

According to this invention, the charging amount of the selected secondary battery is suppressed by reducing the charging current of the selected secondary battery by detecting the amount of charge rate deviation between the secondary batteries during charging. Thus, the charge amount difference between the batteries constituting the assembled battery can be reduced to approach the uniform charge state. For this reason, when the power of the secondary battery is used shortly after the end of charging, there is no opportunity for discharging after the end of charging, but even in such a case, the selected secondary battery is being charged. By suppressing the amount of charge, it is possible to equalize the charged state of a plurality of secondary batteries and provide a very useful assembled battery device.

According to claim 4, in addition to the invention of claim 3, computing device further after completion of charging, the charging rate is the difference in charging rate between the secondary cell from the charging rate determined for each of the secondary batteries The secondary battery selected to determine the amount of deviation of the battery and to suppress the amount of deviation of the charging rate is discharged.

According to the present invention, in addition to the charge amount control during charging performed in the invention of claim 3, the charge is suppressed in the charge amount control during the charge by discharging the selected secondary battery after the end of the charge. When the rate is not sufficiently equalized, it is possible to provide a useful discharge step that can eliminate this state.

  According to claim 5, the positive electrode of the secondary battery includes a lithium metal phosphate having an olivine structure. According to the present invention, it is preferable to secure a range in which capacity detection based on voltage is possible in a high charge / discharge capacity region. In addition, since the lithium metal phosphate having an olivine structure hardly generates oxygen in an overload state such as a high temperature, it contributes to providing an assembled battery that is thermally and chemically stable.

According to claim 6, the lithium metal phosphate is a compound represented by LiMPO ₄ , and M is preferably at least one metal element selected from Mn, Fe, Co, and Ni.

  According to claim 7, the M is preferably a metal element of Mn or Fe. According to the present invention, by providing lithium metal phosphate having metal elements of Mn and Fe as a positive electrode active material, a battery pack having at least two low change regions can be provided.

  According to claim 8, the negative electrode of the secondary battery preferably includes any one of lithium metal, carbon-based material, titanium oxide, and alloy-based material.

It is the schematic which showed the structure of the assembled battery apparatus to which this invention is applied. It is a figure which shows the charging characteristic per secondary battery of the assembled battery contained in an assembled battery apparatus. It is a flowchart which shows the process sequence of the charge driving | operation which concerns on 1st Embodiment. 4 is a subroutine showing a processing procedure of a “SOC equalization control” step in the flowchart of FIG. 3. It is a flowchart which shows the process sequence of the charge driving | operation which concerns on 2nd Embodiment. 6 is a subroutine showing a processing procedure of a “SOC equalization control” step in the flowchart of FIG. 5. It is a figure which shows the charge characteristic per secondary battery of the assembled battery which concerns on 3rd Embodiment. It is a flowchart which shows the process sequence of the charge driving | operation which concerns on 3rd Embodiment. It is a figure which shows the charge characteristic per secondary battery of the assembled battery which concerns on 4th Embodiment. It is a flowchart which shows the process sequence of the charge driving | operation which concerns on 4th Embodiment. It is a flowchart which shows the process sequence of the charge driving | operation which concerns on 5th Embodiment.

(First embodiment)
A first embodiment to which an assembled battery device according to the present invention is applied will be described. The assembled battery device 200 includes a plurality of lithium ion secondary batteries having a charging characteristic having a low change region in which a voltage change width with respect to an SOC (state of charge, charge state, or charge rate indicating a charge state) is equal to or less than a predetermined value. A battery 10 (hereinafter also simply referred to as “secondary battery 10”) and the voltage and current detected for the secondary battery 10 during charging of the secondary battery 10 are used to generate the secondary battery 10. And an arithmetic unit 42 for calculating the state of charge stored in the battery.

  The assembled battery 100 is configured by connecting a plurality of secondary batteries 10 in series. The assembled battery 100 can be used as a battery mounted on, for example, an electric vehicle (EV) that runs only by an electric motor, a plug-in hybrid vehicle (PHV) that uses a motor and an internal combustion engine as a driving force, and the like. .

  FIG. 1 is a schematic diagram showing a configuration of an assembled battery device 200 to which the present invention is applied. The assembled battery device 200 is mounted on, for example, a hybrid vehicle and connected to an electric motor for traveling. As shown in FIG. 1, the assembled battery device 200 includes an assembled battery 100, a current detection device 20, a voltage detection device 30, and a battery control device 40.

  The battery control device 40 includes an input unit 41, a calculation device 42, a storage unit 43, an output unit 44, and the like. The current detection device 20 detects the value of current flowing through the plurality of secondary batteries 10 constituting the assembled battery 100. The voltage detection device 30 detects the voltage between the terminals of each secondary battery 10. The current value detected by the current detection device 20 and the terminal voltage detected by the voltage detection device 30 are input to the input unit 41. The SOC is obtained by the computing device 42 by computation using, for example, a map stored in the storage unit 43, a predetermined program, or the like. The computing device 42 uses a voltage between the terminals detected by the voltage detection device 30 and a map (for example, see FIG. 2) showing the charging characteristics specific to the assembled battery 100 stored in the storage unit 43, for a predetermined program. Thus, the SOC (charged state) stored in the assembled battery 100 is obtained by calculation according to the above. FIG. 2 is a charging characteristic diagram showing a charging characteristic per secondary battery of the assembled battery 100 included in the assembled battery device 200.

  The output unit 44 controls charging of the assembled battery 100 based on the calculation result. Therefore, the battery control device 40 detects the state of charge, that is, the SOC, using the current value flowing through the entire assembled battery 100 or each secondary battery 10, the voltage between terminals in each secondary battery 10, and the like. The charging of the battery pack 100 is controlled using the SOC.

  The secondary battery 10 has a low change region in which a voltage change width with respect to the SOC is equal to or less than a predetermined value (for example, 0.4 V or less) in a specific charge characteristic diagram showing a charge characteristic related to the SOC and the inter-terminal voltage during charging Have For example, as shown in FIG. 2, the inter-terminal voltage per secondary battery constituting the assembled battery 100 has a low change region in which the voltage change width with respect to the SOC is 3.25 V to 3.45 V. According to the assembled battery 100 in which the secondary batteries 10 having such characteristics are connected in series, accurate detection of the state of charge of the battery can be reliably realized with stable output characteristics (IV characteristics).

  The relationship between the SOC and the voltage per secondary battery and the time change rate dV / dt of the voltage is shown, for example, in the charge characteristic diagram of FIG. The charging characteristic diagram includes a first high change region having a large voltage change width in a range of SOC of 0% to about 7%, and a voltage change width of a predetermined range of SOC in a range of about 7% to about 95%. It has a low change region that is less than or equal to the value (0.2 V or less), and has a second high change region with a large voltage change width in the SOC range of about 95% to 100%. The low change region is a voltage flat region in which the voltage change amount is small and the voltage increase curve is gentle.

  In the upper part of FIG. 2, the change of the time change rate dV / dt of the voltage with respect to the SOC is shown for the voltage flat region. The change of dV / dt has two ranges exceeding a predetermined threshold value Vth. The two ranges are, for example, a SOC range of 15% to 35% and a range of 75% to 80%. Of the two ranges, the range with the smaller SOC is P1 point where dV / dt tends to exceed the predetermined threshold Vth as the SOC increases, and tries to fall below the predetermined threshold Vth as the SOC increases. It is a range between P2 points. Of the two ranges, the range with the higher SOC is P3 point where dV / dt tends to exceed the predetermined threshold Vth as the SOC increases, and tries to fall below the predetermined threshold Vth as the SOC increases. It is a range between P4 points. In addition, these two ranges are specific to the secondary battery 10 that does not fluctuate due to battery deterioration accompanying an increase in the number of times of charging.

  The SOC of the assembled battery 100 is obtained from the specified SOC values associated with each of the four P1 points to P4 points when a predetermined condition is satisfied, and the SOC calculation obtained by current integration is performed. Is required.

  In the present embodiment, specifically, as shown in FIG. 2, when the arithmetic device 42 performs charging in the low change region, the time change rate dV / dt of the voltage is predetermined for a predetermined time. When the threshold value Vth is exceeded, the SOC of the secondary battery 10 is determined to be a predetermined SOC value associated with the threshold value Vth in advance (for example, the SOC associated with the P1 point or the P3 point). That is, the arithmetic device 42 determines the SOC after a predetermined time has elapsed after the time rate of change dV / dt of the voltage exceeds the threshold value Vth as a predetermined specified value associated with the threshold value Vth in advance. The SOC of the secondary battery 10 is detected.

  The lithium ion secondary battery 10 includes a positive electrode, a negative electrode, an electrolyte interposed between the positive and negative electrodes, and other necessary members. Hereinafter, each element will be described.

(Positive electrode)
As the positive electrode active material included in the lithium ion secondary battery 10, it is desirable to use an olivine type lithium compound having an olivine structure, for example, a lithium metal phosphate which is one of phosphoric acid compounds. The lithium metal phosphate is, for example, a compound represented by LiMPO ₄ . The M is preferably at least one metal element selected from Mn, Fe, Co, and Ni.

  More preferably, M is a metal element of Mn or Fe. If such a metal element is used, the operating voltage range does not become large in the charge / discharge characteristic diagram, and it can be set to an appropriate range, and an effective and easy-to-handle secondary battery for SOC detection is provided. be able to.

  Other elements that can be included include a conductive material, a binder, and a current collector. The positive electrode active material can form an active material layer formed in layers on the surface of the current collector in a state of being mixed with a conductive material, a binder, and the like. For example, the positive electrode active material, the binder, the conductive material, and the like can be formed by mixing them in a solvent such as water or N-methyl-2-pyrrolidone (NMP) and then applying the mixture on the current collector.

  The conductive material is a material that transmits and receives electrons generated from the active material, and may be any material that has conductivity. Examples thereof include a carbon material and a conductive polymer material. As the carbon material, ketjen black, acetylene black, carbon black, graphite, carbon nanotube, amorphous carbon and the like can be adopted. Further, polyaniline, polypyrrole, polythiophene, polyacetylene, or polyacene can be used as the conductive polymer material.

  The binder is a material that forms an electrode by combining components such as an active material. Various polymer materials can be adopted, and those having high chemical and physical stability are desirable. Examples thereof include polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene rubber (EPDM), styrene butadiene rubber (SBR), nitrile rubber (NBR), and fluorine rubber. Further, when a conductive polymer material is employed as the conductive material, the action of the binder can be expressed in addition to the action of the conductive material. The current collector may be a metal foil formed from a metal such as aluminum.

(Negative electrode)
Although the structure of a negative electrode is not specifically limited, It can have a suitable negative electrode active material. Depending on the type of the negative electrode active material, a binder or a current collector may be used. The binder can be the same as that described for the positive electrode. The current collector may be a metal foil formed of a metal such as copper.

  When the lithium ion secondary battery 10 is configured, a compound capable of inserting and extracting lithium ions can be used alone or in combination as the negative electrode active material. Examples of compounds capable of inserting and extracting lithium ions include metal materials such as lithium, alloy materials containing silicon, tin, copper and the like, carbon materials such as graphite and coke, and titanium oxide. Further, as the titanium oxide, those having a bronze structure and those not having a bronze structure can be adopted. Accordingly, the negative electrode of the lithium ion secondary battery 10 includes any one of lithium metal, carbon-based materials such as graphite, titanium oxide, and alloy-based materials. In addition, these active materials can be used not only alone but also in a mixture of a plurality of types.

  For example, when a lithium metal foil is used as the negative electrode active material, it can be formed by pressure bonding the lithium foil to the surface of a current collector made of a metal such as copper. When an alloy material or a carbon material is used as the negative electrode active material, the negative electrode active material and a binder are mixed in a solvent such as water or NMP, and then applied onto a current collector made of a metal such as copper. Can be formed.

(Electrolytes)
The electrolyte is a medium that transports charge carriers such as ions between the positive electrode and the negative electrode, and is not particularly limited, but is physically, chemically, and electrically stable in an atmosphere in which the lithium ion secondary battery 10 is used. Things are desirable.

For example, as the electrolyte, LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO An electrolytic solution in which at least one selected from ₂ ) is used as a supporting electrolyte and dissolved in an organic solvent is preferable. Examples of the organic solvent include propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and mixtures thereof. Among them, an electrolytic solution containing a carbonate solvent is preferable because of its high stability at high temperatures. In addition, a solid polymer electrolyte containing the above electrolyte in a solid polymer such as polyethylene oxide, a polymer material having lithium ion conductivity, a solid electrolyte such as ceramic or glass can also be used.

(Other necessary components)
As other necessary members, a separator, a case, an electrode terminal, and the like are selected according to the configuration and usage of the secondary battery.

  It is desirable to interpose a separator that is a member that achieves both electrical insulation and ion conduction between the positive electrode and the negative electrode. When the electrolyte is liquid, the separator also serves to hold the liquid electrolyte. As the separator, a porous synthetic resin film, in particular, a porous film made of polyolefin polymer (polyethylene, polypropylene) or glass fiber, or a nonwoven fabric can be employed. Furthermore, it is preferable that the separator adopts a larger size than the positive electrode and the negative electrode for the purpose of ensuring insulation between the positive electrode and the negative electrode.

  In general, the positive electrode, the negative electrode, the electrolyte, the separator, and the like are housed in some case. The case is not particularly limited, and can be made of various materials and forms. The case is provided with electrode terminals for transmitting and receiving electric power inside and outside the case.

  Next, a charge control method for controlling charging of the assembled battery 100 in the assembled battery device 200 will be described with reference to the flowchart of FIG.

  First, in step 10, when charging of the plurality of secondary batteries 10 constituting the assembled battery 100 is started under the control of the battery control device 40, the process proceeds to step 20 where the current values detected by the current detection device 20 are integrated. Then, the SOC of the secondary battery 10 is calculated. Next, in step 30, it is determined whether or not the calculated SOC is less than 50% and the time rate of change dV / dt of the voltage based on the voltage V detected by the voltage detection device 30 exceeds the threshold value Vth for a predetermined time. .

  If the condition of step 30 is determined to be YES, the SOC is set to the value of point P1 in step 40. Thus, after confirming that dV / dt exceeds the threshold value Vth for a predetermined time, the SOC is defined as a value corresponding to the P1 point. In other words, in the SOC setting process, the dV / dt is checked a plurality of times (for example, 10 times) by passing a state where the dV / dt exceeds the threshold value Vth for a predetermined time (for example, 1 second), and then the SOC is set to P1. It is specified to be 15% corresponding to the point.

  In step 50, the SOC of the secondary battery 10 is calculated by integrating the current values detected by the current detection device 20. Next, in step 60, it is determined whether or not the calculated SOC is 50% or more and the time change rate dV / dt of the voltage based on the voltage V detected by the voltage detection device 30 exceeds the threshold value Vth for a predetermined time. .

  If it is determined that the condition of step 60 is NO, the process returns to step 50, and the SOC is calculated by current integration. If YES is determined in the step 60, the SOC is set to a value of the point P3 in a step 70. Thus, after confirming that dV / dt exceeds the threshold value Vth for a predetermined time, the SOC is defined as a value corresponding to the point P3. In other words, the SOC setting process checks the dV / dt a plurality of times (for example, 10 times) by passing the state where the dV / dt exceeds the threshold value Vth for a predetermined time (for example, 1 second), and then sets the SOC to P3. It is prescribed to 75% corresponding to the point.

  In step 80, the SOC of the secondary battery 10 is calculated by integrating the current values detected by the current detection device 20. Next, in step 90, the battery control device 40 determines whether or not the calculated SOC of the secondary battery 10 has reached a charge upper limit voltage (for example, a charge set value). This determination is repeated until the SOC reaches the charge upper limit voltage. If the battery control device 40 determines YES in step 90, the battery control device 40 stops charging and executes a process of setting the SOC to 100%.

  After the end of charging, SOC equalization control for equalizing the SOC is executed for all the secondary batteries 10 constituting the assembled battery 100 in step E1, and the flowchart of FIG. 3 is ended.

  If it is determined NO in step 30 above, then in step 32, the calculated SOC is 50% or more, and the voltage temporal change rate dV / dt based on the voltage V detected by the voltage detection device 30 sets the threshold value Vth to a predetermined value. It is determined whether or not the time is exceeded.

  If it is determined that the condition of step 32 is NO, the process proceeds to step 34, and the battery control device 40 determines whether or not the calculated SOC of the secondary battery 10 has reached a charge upper limit voltage (for example, a charge set value). If it determines with YES at step 34, the battery control apparatus 40 will progress to step 100, will perform SOC equalization control, such as a charge stop, and will complete | finish the flowchart of FIG. If NO in step 34, the process returns to step 20. On the other hand, if the condition of step 32 is determined to be YES, the process proceeds to step 70, the subsequent steps are sequentially executed, and the flowchart of FIG.

  Next, the “SOC equalization control” step of step E1 of FIG. 3 will be described according to the subroutine of FIG.

First, at step E10, the SOC is set to a value (75%) corresponding to the point P3. In step E11, to start calculation of the SOC for all secondary batteries 10 constituting the battery pack 100, or to the next, it is at step E13, SOC for all the cells at least 75% corresponding to the point P3 Determine whether or not.

  If it determines with NO by step E13, bypass discharge will be implemented about the battery determined as SOC being 75% or more (step E14). The bypass discharge is performed in Step E15 until the SOC of the equalization target battery reaches 75% corresponding to P3. If YES is determined in step E15, the present subroutine is terminated.

  If YES is determined in step E13, the secondary battery 10 having the lowest SOC is determined in step E16, and the SOC deviation amount (difference from the secondary battery 10 having the lowest SOC is determined for each of the other secondary batteries 10). The amount of charge state deviation) is calculated. Then, it is determined whether any of the SOC deviation amounts of the secondary batteries 10 is equal to or greater than a predetermined value DSOC.

  If NO is determined in step E16, there is no battery cell that needs to be subjected to SOC equalization, and thus this subroutine is terminated. If YES is determined in step E16, bypass discharge is performed only for the secondary battery 10 determined to be YES in step E16 and selected as the target of equalization processing (step E17). The bypass discharge is performed until it is determined in step E18 that the SOC of the battery to be equalized has become equal to the minimum SOC. If YES is determined in the step E18, the present subroutine is terminated.

  As described above, in the SOC equalization control step, after completion of charging, the charge capacity difference is bypass-discharged for each secondary battery 10, and the SOC of the plurality of secondary batteries 10 is changed to the secondary battery having the lowest SOC. In addition, equalization is achieved.

  The effect which the assembled battery apparatus 200 of this embodiment brings is demonstrated. The assembled battery device 200 includes a plurality of secondary batteries 10 having a charging characteristic having a low change region in which a voltage change width with respect to the SOC (charged state) is a predetermined value or less, and charging the secondary battery 10. And an arithmetic unit 42 that calculates the SOC of the secondary battery 10 using the voltage detected for the secondary battery 10 or the like. When performing the charging in the low change region, the arithmetic device 42 determines the SOC of the secondary battery 10 in advance when the voltage time change rate dV / dt exceeds a predetermined threshold value Vth for a predetermined time. A predetermined SOC value is determined in advance that is associated with the predetermined threshold value Vth (steps 40 and 70).

  According to this, when the time change rate of the voltage or the change rate of the electric quantity of the voltage satisfies a predetermined condition corresponding to each, the state of charge of the secondary battery is determined as a predetermined value of the charge state associated in advance. Thus, the state of charge of the secondary battery is detected with high accuracy. Therefore, it is possible to provide the assembled battery device 200 that enables highly accurate detection of the state of charge in a region of stable output characteristics in which voltage fluctuation is small with respect to changes in SOC. In addition, in order to enable highly accurate SOC detection during charging as described above, it is not necessary to stop charging for SOC detection, and the time until charging is completed can be shortened and used effectively.

  In addition, in order to enable highly accurate SOC (charge state) detection in a low change region, it is possible to detect variations in SOC between batteries not only in the vicinity of full charge but also in a wide charge capacity range.

  After the end of charging, the arithmetic device 42 determines the SOC shift amount (charge state shift amount), which is the difference in SOC between the secondary batteries, from the SOC obtained for each of the secondary batteries 10, and the SOC shift amount. The secondary battery 10 selected to suppress the discharge is discharged (steps E14 and E17).

  According to this control, after the end of charging, by performing discharge on the selected secondary battery 10, due to the degree of progress of deterioration of the individual batteries, it is possible to improve the state that was not uniformly charged, This also contributes to the suppression of battery deterioration. Moreover, since it is possible to determine the variation in the SOC in a wide charge capacity range other than the vicinity of the full charge, there is an effect that it is possible to suppress the deterioration of the secondary battery 10.

  Moreover, the positive electrode of the lithium ion secondary battery 10 contains a lithium metal phosphate having an olivine structure. This is preferable in securing a range in which capacity detection based on voltage is possible in a high charge capacity range. In addition, since the lithium metal phosphate having an olivine structure hardly generates oxygen in an overload state such as a high temperature, a thermally and chemically stable assembled battery 100 can be obtained.

  Further, M is preferably a metal element of Mn or Fe. According to this, by providing lithium metal phosphate having metal elements of Mn and Fe as a positive electrode active material, a voltage fluctuation range formed by at least two high voltage change regions in the charge / discharge characteristic curve is obtained. Can be suppressed. When the voltage fluctuation range is large, the stability of the output characteristics of the assembled battery is lowered, and the decomposability of the electrolytic solution is increased, and the battery may not function when it is decomposed. Therefore, the effective assembled battery 100 can be obtained from the viewpoint of both the stability of the output characteristics of the assembled battery 100 and the detectability of the charge / discharge capacity due to the suppression effect of the voltage fluctuation range.

(Second Embodiment)
In the second embodiment, characteristic charge control described in the second embodiment will be described with reference to FIGS. 5 and 6 as another form of charge control described in the first embodiment. FIG. 5 is a flowchart showing a processing procedure of the charging operation according to the second embodiment. FIG. 6 is a subroutine showing the processing procedure of the “SOC equalization control” step in the flowchart of FIG. The configuration, control, and the like that are not particularly described in the present embodiment are the same as those in the first embodiment, and the effects thereof are also the same.

  The characteristic charge control described in the present embodiment is different from the charge control of the first embodiment in that the “SOC equalization control” in step E2 is executed not during the end of charging but during charging. Further, in accordance with this difference, the “SOC equalization control” subroutine is performed according to FIG.

  Hereinafter, differences from the charge control of the first embodiment will be described. In the flowchart of the second embodiment, after step 70 and before determining whether or not the SOC has reached the charging upper limit voltage in step 90, that is, after the start of charging and before the end of charging, the assembled battery in step E2. For all the secondary batteries 10 constituting 100, SOC equalization control for equalizing SOC is executed.

  The “SOC equalization control” step of step E2 will be described according to the subroutine of FIG. First, in step E20, the SOC is set to a value (75%) corresponding to the point P3. Next, in step E21, the calculation of the SOC is started for all the secondary batteries 10 constituting the assembled battery 100. In step E22, the secondary battery 10 having the lowest SOC is determined, and for each of the other secondary batteries 10, an SOC shift amount (a charge state shift amount) that is a difference from the secondary battery 10 having the lowest SOC is calculated. To do. Then, it is determined whether any of the SOC deviation amounts of the secondary batteries 10 is equal to or greater than a predetermined value DSOC.

  If NO is determined in step E22, there is no battery cell that needs to equalize the SOC, and thus this subroutine is terminated. If it determines with YES by step E22, bypass charge will be implemented only about the secondary battery 10 by which it determined with YES by previous step E22 and was selected as the object of the equalization process (step E23).

  Bypass charging is to reduce the amount of charge to the secondary battery by causing the current to flow through the electrical resistance to the secondary battery to reduce the charging current. By this bypass charging, from the viewpoint of the SOC of the secondary battery, the same effect as the above-described bypass discharge of suppressing the SOC can be obtained. The bypass charging is performed until it is determined in step E24 that the SOC of the equalization target battery is less than the predetermined value DSOC. If YES is determined in the step E24, the present subroutine is terminated.

  As described above, in the SOC equalization control step, during charging, the charge amount is suppressed for the secondary battery 10 whose charge capacity is larger than the other battery by a predetermined amount or more. As a result, the SOC of the plurality of secondary batteries 10 is matched with the secondary battery having the lowest SOC, so that the SOCs of the secondary batteries 10 constituting the assembled battery 100 are equalized.

  The effect which the assembled battery apparatus 200 of this embodiment brings is demonstrated. The arithmetic device 42 detects the SOC shift amount between the secondary batteries from the SOC obtained for each of the secondary batteries 10 during charging, and charges the secondary battery 10 selected based on the SOC shift amount. The current is reduced (steps E22 and E23).

  According to this control, the charging amount of the selected secondary battery 10 is suppressed by reducing the charging current of the selected secondary battery 10 by detecting the SOC shift amount between the secondary batteries during charging. And the charge amount difference between the batteries which comprise the assembled battery 100 can be made small, and it can approach an equal charge state. For this reason, when the power of the secondary battery 10 is used shortly after the end of charging, there is no opportunity for discharging after the end of charging. Even in such a case, the selected secondary battery 10 By suppressing the amount of charge during charging, the SOC of the plurality of secondary batteries 10 can be equalized.

  Further, the amount of SOC shift between the secondary batteries detected during charging or after the end of charging is determined by detecting the secondary battery 10 with the lowest SOC and the difference between the SOC of each of the other secondary batteries 10 and the lowest SOC. Based on this, the secondary battery 10 that is a target for reducing the charging current is selected. According to this process, since the charge amount of the selected secondary battery 10 is matched with the lowest SOC, the charge amount difference between the batteries constituting the assembled battery 100 can be almost eliminated and an equal charge state can be achieved. Therefore, it is possible to provide charge control that makes it difficult for a large difference in the degree of battery deterioration between the plurality of secondary batteries 10 constituting the assembled battery 100.

(Third embodiment)
In the third embodiment, characteristic charge control described in the third embodiment will be described with reference to FIGS. 7 and 8 as another form of charge control described in the first embodiment. FIG. 7 is a diagram illustrating charging characteristics per secondary battery of the assembled battery 100 according to the third embodiment. FIG. 8 is a flowchart showing the procedure of the charging operation according to the third embodiment. The configuration, control, and the like that are not particularly described in the present embodiment are the same as those in the first embodiment, and the effects thereof are also the same.

  As shown in FIGS. 7 and 8, the characteristic charge control described in the present embodiment is different from the charge control of the first embodiment in “SOC calculation method” in step 40A and step 70A.

  Hereinafter, differences from the charge control of the first embodiment will be described. Also in the present embodiment, the arithmetic device 42 uses a voltage between terminals detected by the voltage detection device 30 and a map (see, for example, FIG. 7) showing the charging characteristics unique to the assembled battery 100 stored in the storage unit 43. Thus, the SOC (charged state) stored in the assembled battery 100 is obtained by calculation according to a predetermined program.

  The change in the charge characteristic diagram and the time change rate dV / dt of the voltage shown in FIG. 7 is the same as that shown in FIG. 2 described in the first embodiment. As shown in FIG. 7, the transition of dV / dt has two ranges exceeding a predetermined threshold value Vth, and dV / dt increases in SOC in the smaller range of the two ranges. Accordingly, a predetermined relational expression is associated with a point (corresponding to the point P1 in FIG. 2) about to exceed the predetermined threshold Vth. The predetermined relational expression is a relational expression F1 that is associated with a predetermined threshold value Vth in advance and is satisfied between the voltage time change rate dV / dt and the state of charge SOC, and is stored in the storage unit 43 in advance. ing.

  Further, a point where dV / dt tends to exceed a predetermined threshold Vth as the SOC increases (corresponding to the point P3 in FIG. 2) in the larger SOC range of the two ranges has a predetermined relationship. An expression is associated. The predetermined relational expression is a relational expression F3 that is associated with a predetermined threshold value Vth in advance and is satisfied between the voltage time change rate dV / dt and the state of charge SOC, and is stored in the storage unit 43 in advance. ing. These predetermined relational expressions are approximate expressions in which a point from the point exceeding the threshold Vth to the inflection point is represented by a straight line or a polynomial curve.

  In the present embodiment, the predetermined relational expressions F1 and F3 are represented by the following expressions, respectively.

(F1) dV / dt = (5.96 × 10 ⁻⁶ ) × SOC (%) − 7.33 × 10 ⁻⁵
(F3) dV / dt = (2.84 × 10 ⁻⁶ ) × SOC (%) − 1.93 × 10 ⁻⁴
Specifically, as shown in FIG. 7, when the arithmetic unit 42 performs charging in the low change region, the time change rate dV / dt of the voltage exceeds a predetermined threshold Vth for a predetermined time. In this case, the SOC of the secondary battery 10 is determined based on the SOC calculated using a predetermined relational expression associated with the threshold value Vth in advance, that is, the F1 expression and the F3 expression. That is, the arithmetic unit 42 determines the SOC after a predetermined time has elapsed since the time rate of change dV / dt of the voltage exceeds the threshold value Vth as the value of the SOC calculated from the predetermined relational expression. The SOC of the battery 10 is detected.

  As shown in FIG. 8, in the flowchart of the third embodiment, after determining “YES” in step 30, in step 40 </ b> A, the SOC is calculated using the above F1 equation, and the SOC in the state satisfying the condition of step 30 is calculated. Set to the value calculated by Formula F1. Furthermore, in the flowchart of the third embodiment, after determining YES in Step 60, in Step 70A, the SOC is calculated using the above F3 equation, and the SOC in the state satisfying the condition of Step 60 is calculated by the F3 equation. Set the value to

  The effect which the assembled battery apparatus 200 of this embodiment brings is demonstrated. The assembled battery device 200 includes a plurality of secondary batteries 10 having charging characteristics including a low change region in which a voltage change width with respect to the SOC (charged state) is equal to or less than a predetermined value, and charging the secondary battery 10 And an arithmetic device 42 that calculates the SOC stored in the secondary battery 10 using the voltage and current detected for the secondary battery 10. The arithmetic unit 42 determines the SOC of the secondary battery 10 in advance when the time change rate dV / dt of the voltage exceeds a predetermined threshold Vth for a predetermined time when charging is performed in the low change region. The SOC value calculated from the relational expression (for example, F1 and F3 above) that is previously associated with the threshold value Vth and is satisfied between the voltage time change rate dV / dt and the SOC is determined (steps 40A and 70A).

  According to this, when the predetermined time condition dV / dt of the voltage satisfies the corresponding condition, the SOC of the secondary battery 10 is correlated in advance between the time change rate of the voltage dV / dt and the SOC. By determining the SOC value calculated from the satisfying relational expression (for example, the above F1 and F3), the state of charge of the secondary battery 10 can be detected with high accuracy. Therefore, it is possible to provide the assembled battery device 200 that enables highly accurate detection of the state of charge in a region of stable output characteristics in which voltage fluctuation is small with respect to changes in SOC.

(Fourth embodiment)
In the fourth embodiment, characteristic charge control described in the fourth embodiment will be described with reference to FIGS. 9 and 10 as another form of charge control described in the first embodiment. FIG. 9 is a diagram illustrating charging characteristics per secondary battery of the assembled battery 100 according to the fourth embodiment. FIG. 10 is a flowchart illustrating a processing procedure of the charging operation according to the fourth embodiment. The configuration, control, and the like that are not particularly described in the present embodiment are the same as those in the first embodiment, and the effects thereof are also the same.

  As shown in FIGS. 9 and 10, the characteristic charge control described in the present embodiment is different from the charge control of the first embodiment in step 30A, step 32A, and step 60A.

  Hereinafter, differences from the charge control of the first embodiment will be described. Also in the present embodiment, the arithmetic device 42 uses a voltage between terminals detected by the voltage detection device 30 and a map (see, for example, FIG. 9) showing the charging characteristics unique to the assembled battery 100 stored in the storage unit 43. Thus, the SOC (charged state) stored in the assembled battery 100 is obtained by calculation according to a predetermined program.

  The secondary battery 10 has a low change region in which a voltage change width with respect to the SOC is equal to or less than a predetermined value (for example, 0.4 V or less) in a specific charge characteristic diagram showing a charge characteristic related to the SOC and the inter-terminal voltage during charging Have Similar to FIG. 2 of the first embodiment, the charging characteristic diagram has a first high change region with a large voltage change width in the range of SOC of 0% to about 7%, and the SOC of about 7% to about 7%. A second high change region having a low voltage change range in which the voltage change width is equal to or less than a predetermined value (0.2 V or less) in a range of 95% and a large voltage change width in a range of approximately 95% to 100% of SOC have.

  In the upper part of FIG. 9, a change in the electric quantity change rate dV / dAh of the voltage with respect to the SOC is shown in the voltage flat region. The change in dV / dAh has two ranges exceeding a predetermined threshold value VAh, and is the same as the change in dV / dt in the first embodiment. The two ranges are, for example, a SOC range of 15% to 35% and a range of 75% to 80%. Of the two ranges, the range with the lower SOC is P1 point where dV / dAh tends to exceed the predetermined threshold VAh as the SOC increases, and tries to fall below the predetermined threshold VAh as the SOC increases. It is a range between P2 points. Of the two ranges, the range with the higher SOC is the point P3 where dV / dAh tends to exceed the predetermined threshold VAh as the SOC increases, and tries to fall below the predetermined threshold VAh as the SOC increases. It is a range between P4 points. In addition, these two ranges are specific to the secondary battery 10 that does not fluctuate due to battery deterioration accompanying an increase in the number of times of charging.

  The SOC of the assembled battery 100 is obtained from the specified SOC values associated with each of the four P1 points to P4 points when a predetermined condition is satisfied, and the SOC calculation obtained by current integration is performed. Is required.

  In the present embodiment, specifically, as shown in FIG. 9, when the arithmetic unit 42 performs charging in the above-described low change region, the electric quantity change rate dV / dAh of the voltage is set in advance for a predetermined time. When the predetermined threshold value VAh is exceeded, the SOC of the secondary battery 10 is determined to be a predetermined SOC value associated with the threshold value VAh in advance (for example, the SOC associated with the P1 point or the P3 point). That is, the arithmetic unit 42 determines the SOC after a predetermined time has elapsed since the rate of change in electric quantity dV / dAh of the voltage exceeds the threshold value VAh to a predetermined specified value that is associated with the threshold value VAh in advance. The SOC of the secondary battery 10 is detected. When charging is performed at a constant current, the change rate dV / dAh of the voltage exhibits the same transition as the change rate dV / dt of the voltage of the first embodiment. In fact, they have the same significance.

  As shown in FIG. 10, in the flowchart of the fourth embodiment, after step 20, in step 30A, the calculated SOC is less than 50%, and the change in the electric quantity of the voltage based on the voltage V detected by the voltage detection device 30 is performed. It is determined whether the rate dV / dAh exceeds the threshold value VAh for a predetermined time. If the condition of step 30A is determined to be YES, the process proceeds to step 40, and if NO is determined, the process proceeds to step 32A.

  In step 32A, it is determined whether or not the calculated SOC is 50% or more and the rate of change dV / dAh of the voltage based on the voltage V detected by the voltage detection device 30 exceeds the threshold VAh for a predetermined time. Similarly, in step 60A, it is determined whether or not the calculated SOC is 50% or more and the rate of change in electric quantity dV / dAh of the voltage based on the voltage V detected by the voltage detection device 30 exceeds the threshold value VAh for a predetermined time. judge.

  The effect which the assembled battery apparatus 200 of this embodiment brings is demonstrated. The assembled battery device 200 includes a plurality of secondary batteries 10 having a charging characteristic having a low change region in which a voltage change width with respect to the SOC (charged state) is a predetermined value or less, and charging the secondary battery 10. And an arithmetic unit 42 that calculates the SOC of the secondary battery 10 using the voltage detected for the secondary battery 10 or the like. When performing the charging in the low change region, the arithmetic device 42 determines the SOC of the secondary battery 10 when the voltage change rate dV / dAh exceeds a predetermined threshold value VAh for a predetermined time. The specified SOC value is determined in advance in association with the predetermined threshold value VAh (steps 40 and 70).

  According to this, the secondary battery 10 is determined to have a predetermined SOC value associated with the secondary battery 10 in a case where a predetermined condition corresponding to the voltage change rate dV / dAh is satisfied. 10 charge states are detected. Therefore, it is possible to obtain the assembled battery device 200 that enables highly accurate detection of the state of charge in the low change region of the output characteristics where the voltage variation is small and stable with respect to the change in the SOC. Further, in order to enable highly accurate SOC detection in a low change region, it is possible to detect variations in SOC between batteries not only in the vicinity of full charge but also in a wide charge capacity range.

(Fifth embodiment)
In the fifth embodiment, characteristic charging control described in the fifth embodiment will be described with reference to FIG. 11 as another form of charging control described in the first embodiment. FIG. 11 is a flowchart showing a processing procedure of the charging operation according to the fifth embodiment. The configuration, control, and the like that are not particularly described in the present embodiment are the same as those in the first embodiment, and the effects thereof are also the same.

  The characteristic charge control described in the present embodiment is different from the charge control of the first embodiment in that “SOC equalization control” executed during the charge in step E2 is further added. This step E2 is performed according to the subroutine of FIG. 6 described in the second embodiment.

  The effects provided by the present embodiment will be described. In addition to the “SOC equalization control” in step E2 performed during charging, the arithmetic unit 42 further shifts the SOC between the secondary batteries from the SOC (charged state) obtained for each secondary battery 10 after the end of charging. (Charging state deviation amount) is determined, and the secondary battery 10 selected based on the SOC deviation amount is discharged (step E1).

  According to this control, in addition to the step (step E2) related to the suppression of the charging amount during charging, the selected secondary battery 10 is discharged after the end of charging, so that the SOC is equalized in step E2. A useful discharge step can be provided that can resolve this condition if not adequately achieved.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the said embodiment, the charging characteristic per secondary battery in the assembled battery 100 is not limited to the form shown in FIG. The charge characteristic shown in FIG. 2 has one low change region in which the voltage change width with respect to the SOC (charged state) is a predetermined value or less. However, the assembled battery 100 according to the present invention may have a charging characteristic having two or more such low change regions. With an assembled battery having such charging characteristics, more points for high-accuracy detection of SOC can be set, so the range in which SOC can be detected with high accuracy can be widened.

10 ... Lithium ion secondary battery (secondary battery)
42 ... arithmetic device 100 ... assembled battery 200 ... assembled battery device

Claims (8)

A plurality of secondary batteries having a charging characteristic having a low change region in which a voltage change width with respect to a charge rate is equal to or less than a predetermined value;
An arithmetic unit that calculates the charge rate stored in the secondary battery using the voltage and current detected for the secondary battery when charging the secondary battery, and
When the charging is performed in the low change region, the arithmetic unit is configured such that when the time change rate of the voltage exceeds a predetermined threshold for a predetermined time, or the voltage change rate of the voltage is set for a predetermined time in advance. The assembled battery device characterized in that, when a predetermined threshold value is exceeded, the detection value of the charging rate of the secondary battery is set to a specified value of the charging rate that is associated in advance with the predetermined threshold value. . A plurality of secondary batteries having charging characteristics including a low change region in which a voltage change with respect to a charging rate is a predetermined value or less;
An arithmetic unit that calculates the charge rate stored in the secondary battery using the voltage and current detected for the secondary battery when charging the secondary battery, and
When performing the charging in the low change region, the arithmetic device, when the time change rate of the voltage exceeds a predetermined threshold for a predetermined time, the detected value of the charge rate of the secondary battery, An assembled battery device, characterized in that it is set to a charge rate value calculated from a relational expression that is associated in advance with a predetermined threshold value and satisfied between the time change rate of the voltage and the charge rate . The arithmetic unit detects a charging rate shift amount, which is a difference in charging rate between the secondary batteries, from the charging rate obtained for each of the secondary batteries during charging , and suppresses the charging rate shift amount. The assembled battery device according to claim 1, wherein a charging current is reduced for the secondary battery selected for the purpose. The arithmetic device further determines the amount of deviation of the charging rate , which is the difference in the charging rate between the secondary batteries, from the charging rate obtained for each of the secondary batteries after the end of charging , and suppresses the amount of deviation of the charging rate. The assembled battery device according to claim 3, wherein the secondary battery selected to be discharged is discharged.   5. The assembled battery device according to claim 1, wherein the positive electrode of the secondary battery includes a lithium metal phosphate having an olivine structure. 6. The lithium metal phosphate is a compound represented by LiMPO ₄ , and M is at least one metal element selected from Mn, Fe, Co, and Ni. Assembled battery device.   The assembled battery device according to claim 6, wherein M is a metal element of Mn and Fe.   The assembled battery device according to any one of claims 1 to 7, wherein the negative electrode of the secondary battery includes any one of lithium metal, a carbon-based material, a titanium oxide, and an alloy-based material. .

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